There are a variety of conditions which result in pathologic chronic collection of bodily fluids within the peritoneum, pleura or pericardial sac. Chronic ascites, pleural effusion and pericardial effusion are conditions in which chronic fluid collections persist and result in increased morbidity and mortality.
These foregoing conditions currently are treated typically by one of three methods: 1) external drainage, which poses a risk of infection and long-term requirement for multiple punctures, 2) drainage to another body cavity, or 3) treatment with drugs. In pleural effusion, excess fluid arising from an underlying pathology, such as lung cancer, breast cancer or lymphoma, accumulates in the pleural cavity. If left untreated, the fluid accumulation may interfere with proper lung function, significantly increasing morbidity and mortality. Depending upon the underlying cause of the pleural effusion, treatment may consist of drug therapy, thoracentesis, in which a needle is periodically inserted through the chest and into the pleural cavity to drain the fluid accumulations, or installation of an intercostal drain, in which one end of a pigtail catheter is inserted into the pleural cavity and the fluid is drained to an external canister. Although a relatively simple procedure, placement of an intercostal drain is associated with a relatively high rate of major complications, including hemorrhage and infection. Repeated effusions also may be treated by pleurodesis, in which two pleural surfaces are attached to one another so that no fluid can accumulate between them. However, this procedure requires a lengthy hospital stay and is reported to be associated with the onset of adult respiratory distress syndrome, a potentially life-threatening complication.
In pericardial effusion, fluid accumulates in the pericardial sac and may lead to increased intrapercardial pressure and reduced cardiac output. Where the fluid accumulation interferes with proper heart function, pericardiocentesis may be performed, in which the fluid is drained to an external site through a needle or catheter inserted through the chest wall and into the pericardial sac. For chronic cases, the treatment of choice is formation of a pericardial window. In this highly invasive procedure, a section of the pericardial sac is removed to create a fistula that permits fluid to drain to the abdomen. Although this procedure is usually well tolerated by patients, the pericardial window may close, requiring re-operation.
Ascites is a highly debilitating complication associated with many medical conditions including liver failure, congestive heart failure and certain cancers. Untreated ascites can result in respiratory compromise, compression of the inferior vena cava (a vital blood vessel) and spontaneous bacterial peritonitis (a life-threatening condition). Conventional treatment for ascites includes a regime of drugs and dietary restriction, and for chronic cases, repeated surgical interventions.
Previously known attempts to treat ascites have included indwelling catheters including external ports, squeeze-bulbs and magnetically-driven reciprocating pumps to transfer ascites from the peritoneal cavity into the venous vasculature, through an external port, or into the bladder. For example, U.S. Pat. No. 4,240,434 to Newkirk and U.S. Pat. No. 4,657,530 to Buchwald each describes a squeezable tube-type ascites shunt having an inlet end configured to the placed in the peritoneal cavity and an outlet end configured to be placed in a vein. Rosenblit et al., in an article entitled “Peritoneal-Urinary Drainage for Treatment of Refractory Ascites: A Pilot Study,” J. Vascular & Interv. Radiology, 9(6):998-1005 (November/December 1998) describes a similar squeeze-bulb system having an outlet disposed in the bladder. U.S. Pat. No. 4,610,658 to Buchwald et al. describes an implantable pump for treating ascites that includes a magnetically-driven pump to transfer fluid from the peritoneal cavity to the vasculature system. Such previously known devices suffer from a variety of drawbacks, including fibrous encapsulation, frequent clogging and infection. Such devices provided little improvement over periodic paracenteses, and resulted in increased rates of infection, re-operation or other complications if left in place for any length of time. Moreover, a key drawback of such previously-known systems is the requirement that the patient must repeatedly locate and manually actuate the pumping mechanism on a daily basis. Such activity may be difficult for patients, especially the elderly and obese, and further complicated by an ascites-distended abdomen. Consequently, the difficulty of manipulating such previously-known systems promotes patient non-compliance, in turn leading to clogging and infection.
Such clogging in previously-known systems was especially problematic at an inlet catheter, if provided. An inlet catheter implanted in the peritoneal cavity for treatment of ascites is prone to clogging due to the viscous properties of fluid in the cavity. In addition, inlet catheters are susceptible to clogging due to tissue ingrowth and solid objects within the accumulated fluid.
In view of the above-noted drawbacks of previously-known systems, it would be desirable to provide methods and apparatus for treating ascites and other intracorporeal fluid accumulations using implantable devices that are resistant to clogging.